GTP-binding proteins play crucial roles in the regulation of fundamental processes in cells of all living organisms. In fact, small monomeric GTP-binding proteins have been found in every organism examined thus far. In eukaryotic cells, these proteins are involved in a number of essential processes, such as signal transduction, protein synthesis and translocation or cell cycle regulation. However, perhaps surprisingly, relatively little information is currently available about roles of GTP-binding proteins in prokaryotes. A subfamily of small GTP-binding proteins, including products of obg and cgtA genes from Bacillus subtilis and Caulobacter crescentus respectively, was discovered recently in bacteria. Members of this subfamily are present in diverse organisms ranging from bacteria to humans. On the other hand, functions of these proteins in regulation of cellular processes are largely unknown. Genes coding for these proteins are essential in almost all bacteria investigated thus far. However a viable Vibrio harveyi insertional mutant in the cgtA gene was described recently by us. Therefore, this mutant gives a unique opportunity to study functions of a member of the subfamily of Obg-like proteins. The goal of this work is to investigate roles of the CgtA protein in the regulation of cellular processes. Our preliminary experiments suggest that the cgtA gene product may be involved in regulation of crucial chromosome functions like synchronization of DNA replication initiation, chromosome partition and DNA repair. We plan to perfom both gentic and biochemical studies to learn about processes and mechanisms controlled by CgtA and about biochemical functions of this protein. Since there is a strong similarity between CgtA-like proteins in diverse organisms, including humans, we believe that studies planned by us and described is this application are of general biological significance.

National Institute of Health (NIH)
Fogarty International Center (FIC)
Small Research Grants (R03)
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International and Cooperative Projects 1 Study Section (ICP)
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Sina, Barbara J
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University of Michigan Ann Arbor
Schools of Arts and Sciences
Ann Arbor
United States
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Sikora, Aleksandra E; Zielke, Ryszard; Wegrzyn, Alicja et al. (2006) DNA replication defect in the Escherichia coli cgtA(ts) mutant arising from reduced DnaA levels. Arch Microbiol 185:340-7
Sikora, A E; Zielke, R; Datta, K et al. (2006) The Vibrio harveyi GTPase CgtAV is essential and is associated with the 50S ribosomal subunit. J Bacteriol 188:1205-10
Sikora, A E; Datta, K; Maddock, J R (2006) Biochemical properties of the Vibrio harveyi CgtAV GTPase. Biochem Biophys Res Commun 339:1165-70
Ulanowska, Katarzyna; Sikora, Aleksandra; Wegrzyn, Grzegorz et al. (2003) Role of the cgtA gene function in DNA replication of extrachromosomal elements in Escherichia coli. Plasmid 50:45-52